It is desirable in certain downhole operations to inject two or more fluids into a well so that at a predetermined time and downhole location, the two fluids combine under controlled conditions to effect a desired result. For example, it is sometimes desirable to seal off the well at a certain area, either completely or partially, to prevent or restrict the flow of fluids either from or into the formation at a particular well interval or zone. It is also desirable in some well operations, particularly those of a remedial nature, to prevent vertical flow externally of a casing or liner which is set in the well. This may be done by perforating the casing or liner and injecting a cement or a sealing material from the surface down through the well and into the zone.
It is also advantageous to mix chemicals in situ for other purposes, e.g. certain downhole chemical treatments, admixtures which become explosive when mixed, while the individual chemicals are non-explosive, etc. Certain polymeric materials may be used as sealing materials for downhole applications, by admixing a polymeric material with a catalyst which gels within a predetermined time to a firm impermeable material. The time between the mixing and gelation of such chemicals, can be controlled by the proportion of the catalytic material. It has been found, however, that in such well operations where polymeric material is used to seal off a well zone, mixing the polymer and catalyst at the surface and then pumping the admixed materials down the well to the predetermined downhole location often results in premature gelation due to mechanical difficulties. On the other hand, when the gelation times are retarded greatly, the admixed materials tend to diffuse excessively into the formation and sometimes are washed away by fluid movement in the formation.
Accordingly, it is an object of my present invention to provide a method for mixing in situ two fluids pumped into a well through a tubing or drill pipe.
It is also an object of my present invention to provide a method for initially mixing two fluids downhole and subsequently emplacing the admixture with a very short gelation time, into a well formation within a relatively short time span after mixing.
It is a further object of my present invention to provide apparatus for mixing two fluids downhole and subsequently injecting the admixture into the well formation within a given time span after the two fluids are initially mixed.
It is a further object of my present invention to provide a ported sliding sleeve apparatus for mixing two initially separated fluids such as a polymeric fluid and an activator chemical downhole, by inserting a plug to move the sliding sleeve and change the port alignment of the sliding sleeve tool to effect admixture of the two fluids and subsequent injection of the admixture into the well formation.
It is also an object of my present invention to provide a ball-type mixer apparatus for admixing two fluids such as a polymeric fluid and an activator chemical, downhole, and injecting the admixture into a well formation within a predetermined time after such admixing.